The Microsoft .NET Framework 3.5 is required for Configuration Manager site server installation. For Windows Server 2008, ...

The Microsoft .NET Framework 3.5 is required for Configuration Manager site server installation. For Windows Server 2008, you can download the Microsoft .NET Framework 3.5 from http://go.microsoft.com/fwlink/?LinkId=185604.  For Windows Server 2008 R2, you can enable the Microsoft .NET Framework 3.5 as a feature within Server Manager.